Instrument illumination



Jan. 19, c MacNElL INSTRUMENT ILLUMINATION Filed Nov. 14, 1940 C/auksI-MacWe ll.

Patented Jan. 19, 1943 UNITED STATES PATENT OFFZCE Bendix Aviation Corporation, South Bend, Ind.

a corporation oi Delaware Application November 14, 1940, Serial No. 365,764

2 Claims.

This invention relates to indicating instruments, and particularly to the illumination of the index elements of such an instrument.

Although, in the accompanying drawing, the invention is illustrated in its application to an instrument of the pointer and dial type, it is not limited to such an application, nor are there any limitations other than those which appear uniformly in each of the appended claims.

In certain installations of instruments, it is present day practice to employ electric lights or lamps having bases which attach to a supporting surface in such manner as to cause the light emitting part of the device to be disposed wholly.

or partly beneath, or within, the outer wall or surface of the supporting member or members, and throw a beam of light along a channel or channels parallel to the panel, said channel orchannels being adjacent the index characters of the instrument. The present invention readily lends itself to a comparable arrangement of parts (although not limited thereto) and in fact such an arrangement is shown in the accompanying drawing. However, in lieu of the light directing channels of such prior art devices, I propose to employ the principles of polarization of light rays, as developed and expressed at length in the patents issued to Edwin H. Land and others, among which may be mentioned Patent No. 2,122,178, granted June 28, 1938.

The invention, therefore, has for an object the utilization of polarized light as a means for rendering an indicating instrument more readily readable, under all conditions.

Figure 1 is a side view partially in section taken on line of Fig. 2.

Fig. 2 is a front view of the instrument showing the dial and pointer.

In the drawing reference character I designates the frame or body of an indicating instrument; 2, the disk or dial on which the index characters 4 appear; 3. the pointer, or needle, as it is sometimes called; 8 and l, the electric lamps (of which there may be more) spaced at even intervals about the body I; l and 9, reflecting surfaces of suitable material and finish; l and In, light polarizing windows adapted to polarize, in a single common plane, the light rays falling thereon from light sources Band I; and reference numeral ll designates the instrument cover glass, which is also oi a light polarizing construction (e. g. Polaroid") Pointer 3 and dial chardifiused in all directions, thereby destroying their.

polarizations, and making it possible for the light to pass, without glare, through the cover glass 5 3 (assuming the glass it to he so arranged that minimum light emerges therefrom), and render the instrument characters, and pointer, readily discernible, against a blacked out background.

As an aid to the blacking out of the background, the surface of the dial 2 and the entire interior walls of the instrument are finished in such manner that the polarized light rays imipinging thereupon will be reflected away, and will, when reflected, have a minimum of diffusion. Thus the only light emerging from the instrument will be that which illuminates the index element 3 and reference characters 4.

What I claim is:

1. In an indicating instrument, the combination of a light polarizing cover glass, an illuminated chamber beneath said cover glass, means for illuminating said chamber, said illuminating means including a source of light built into the instrument and located beneath the plane of said cover glass, means for polarizing the light from said source, indicia means in said chamber, and means for depolarizing that portion of the light from said source which strikes said indicia means, said de-polarizing means including multi-edged light diffusing particles applied to said indicia means and serving to d'epolarize said light.

2. In an indicating instrument, thecombination of a light polarizing cover glass, an illuminated chamber beneath said cover glass, means for illuminating said chamber, said illuminating means including a source of light built into the instrument and located beneath the plane of said cover glass, means for polarizing the light from said source, indicia means in said chamber, and means for de-polarizing that portion of the light from said source which strikes said indicia means, said de-polarizing means including multi-edged light diffusing particles coated on said indicia means and serving to de-polarize the light that emerges from said chamber by way of said cover glass.

CHARLES I. MAONTEIL. 

